The invention relates to heat exchangers, especially for motor vehicles.
It relates more particularly to a heat exchanger for heat exchange between a first fluid and a second fluid, comprising a stack of pockets mutually aligned in a longitudinal direction and having two header boxes that are mutually juxtaposed in a lateral direction and are each formed by the alignment, in the longitudinal direction, of inlet or outlet chambers belonging respectively to the different pockets, the header boxes as a whole being divided into at least three connecting channels, and in which exchanger the first fluid is injected into an upstream connecting channel by a longitudinal nozzle passing through a heat exchanger end face remote from the upstream connecting channel, and at least one other connecting channel formed by other pockets.